X is a variable that depends upon plant size, veg time, training technique, etc.
For example, a SOG grower would be happy with half a zip off a clone flowered the moment it's rooted in a quart pot. You'd need to take down 32 of these per month. But a SCROG grower would harvest a SINGLE PLANT to get that. Get it?
The constant is light:

0.5 grams per watt of HID light in the flower room per month of flower